I built a MIDIBox SID V1 back in 2005 and got it working.  I also built a MIDIBox FM but never got as far as even powering it up, and I bought parts for an early revision of the sequencer but didn't get anywhere with that.  I ended up not having the budget for cases, panels and knobs - and my keyboard only has USB MIDI so I have to route things through my computer to use any of this and it was just too big of a hassle at the time and life got in the way of making it better.   Now a few year